Fertilization:

Mature Oocyte Structure

The mature Xenopus oocyte is far from homogeneous. Various
components have spatially specific distributions. Among the most
obvious are yolk platelets. Varying in size, density and location,
yolk platelets
are one of the most obvious indications that the oocyte has
lots of structure. There are other inhomogeneities in the oocyte,
however. These include maternal
messenger RNAs, such as Vg1,
which localizes to the extreme vegetal
pole of the oocyte.

A schematic diagram of the yolk distribution in the mature
Xenopus oocyte.